What Is Light?The simplest definition of light is “visually perceived radiant energy". “Visible” light is just a small segment of the electromagnetic spectrum— a broad range of radiant energy which also includes X-rays, ultraviolet and infrared energy, micro-waves and radio waves. Any form of electromagnetic energy, including light, radiates outward from its source in straight lines at “the speed of light” (300,000 kilometers per second) and dissipates as it gets further from its source.
As visually perceived radiant energy, light powers the mechanism of sight. It is light, reflected from objects to our eyes, that allows us to see. Of all our senses, sight is the most dominant, controlling and defining how people perceive the world. And yet it’s impossible to prove that any two people see a given object in exactly the same way. In fact, it often seems that visual perception—an individual’s response to light—is extremely subjective. This makes it difficult to define and measure specific attributes of light. Furthermore, changes in light can change people’s perceptions. A dark alley, for example, provokes an entirely different reaction than one that is brightly lit. Lighting, therefore, can have a profound effect on people’s emotions and how they respond to an environment.
Light and ColorLight and color are inextricably connected; in a sense, light is color. The visible spectrum of electromagnetic energy is a range. Light at one end has a shorter wavelength and appears violet. Light at the other end has a longer wavelength and appears red. All other colors— blue, blue-green, green, yellow and orange— appear in the middle. Light that features all the visible wavelengths in roughly equal amounts appears white. Note, however, that these quantities do not have to be precise. The various wavelengths within a given light source—its “color makeup”— can vary greatly and it will still appear white.
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